docs: def timeline(self, request, drip_id, into_past, into_future):
          """
          Return a list of people who should get emails.
          """
          from django.shortcuts import render, get_object_or_404
  
          drip = get_object_or_404(Drip, id=drip_id)
  
          shifted_drips = []
          seen_users = set()
          for shifted_drip in drip.drip.walk(into_past=int(into_past), into_future=int(into_future)+1):
              shifted_drip.prune()
              shifted_drips.append({
                  'drip': shifted_drip,
                  'qs': shifted_drip.get_queryset().exclude(id__in=seen_users)
              })
              seen_users.update(shifted_drip.get_queryset().values_list('id', flat=True))
  
          return render(request, 'drip/timeline.html', locals())